The number of emails you are able to send depends on the type of plan you are on.
As the number of emails you can send varies, you can check for your specific case by going to your 'Campaign Settings' and clicking on 'Outreach Schedule'.
On this page, you can view the Daily Limit for your campaign. There is a limit of sending 150 emails per day per campaign, but this can be reduced according to your preferred outreach schedule.
To view how many emails you have sent out during the current billing cycle, visit your 'Billing & Plans' page.